Power windows are now commonly offered in many motor vehicles such as automobiles and trucks. Such power windows usually incorporate at least one DC motor for driving the window up and down in response to an operator actuatable switch. The current required to drive such motors is usually fairly high, and most often well above that which would ordinarily be capable of being transmitted by printed circuit boards. As is well known, conventional printed circuit boards have traditionally been limited to low current applications where currents are kept generally below about 0.5 amps. The current typically required for driving motors associated with power window control circuits is generally ranges from about 20 to 80 amps.
Heretofore, the standard approach to automotive switch control design has involved insert molding technology. This involves using a plurality of independent brass or copper lead frames (i.e., conductors) to carry high electrical current between a vehicle wiring harness and the switch contacts of an operator accessible switch control. These lead frames are typically imbedded in a plastic body or substrate. This process generally requires specialized injection mold tooling and techniques which can accommodate variously shaped and sized lead frames. Frequently, "two shot" molding is required in which the plastic material above and below the portions of the lead frame is injected into the mold in sequential steps. Such apparatus and procedures are relatively expensive and time consuming and add to the complexity and cost of power window control circuits in view of the increased tooling expense required to produce such assemblies. Also, the plastic body portion described above is typically restricted to accommodating only the lead frames and associated switch contacts. Thus, a separate printed circuit board is typically needed for the electronic components of the control circuit. This also significantly increases the overall cost of the control circuit.
In the conventional applications of a power window switch for an automobile, an operation of a power source has been conducted by a construction of mechanical seesaw type as it were, because of direct make and break of a load using alloy contacts the excessive starting current which occurs at the initial switching causes an arc discharge when alloy contacts contact each other, and for this reason faces of a traveling contact and a fixed contact are damaged to be uneven so a contact operation becomes unstable, and repeated operations shorten the life of a switch. Besides the shortcoming above mentioned conventional mechanical power window switches have another shortcoming. Conventional switches use an elastic spring in order to return a button once pushed so the touch is not agreeable.
Another power window switch is shown in U.S. Pat. No. 4,899,063 to Suck. In Suck, a power window switch for an automobile having a switching mechanism which includes a fixed contact plate and a circuit board secured within the inside of a resinous casing, the casing including a port. Positioned above the port is a button which includes a sloped elastic portion having its outer edge secured to the casing around the port. Compression of the button's sloped elastic portion places a conductive rubber contact attached to the bottom surface of the button into contact with a fixed contact on the fixed contact plate. The circuit board includes a switching circuitry which is responsive to variations in position of the button and attached conductive rubber contact.
Another is shown in U.S. Pat. No. 5,412,166 to Krupp. A power switch control module for a power window control circuit of a motor vehicle. The control module incorporates a printed circuit board, a plurality of switch contacts secured to the printed circuit board, a plurality of connector terminals also secured to the printed circuit board, a plurality of high current traces formed on an upper surface of the printed circuit board for coupling selected pairs of the switch contacts and connector terminals electrically together, and a switch control. The switch control is mounted in a frame member for pivotal movement relative to the printed circuit board and is movable between up and down positions. When in the up position the switch control electrically couples a first selected pair of switch contacts and when in the down position the switch control electrically couples a second selected pair of the switch contacts. The high current traces are capable of handling about 20-80 amps of current. Since the high current traces are formed on the upper surface of the printed circuit board, no injection molding, tooling or techniques are required for construction of the module as typically required with prior art control modules. Also, the undersurface of the printed circuit board can advantageously be used to mount other electronic components of the control circuit.
Angular or linear travel on window lift switches is accomplished by rocker or toggle switches which require more travel than low profile snap domes or snap switch blades will allow. That travel is typically 4-6 degrees. However, a design may require as much as 18 degrees travel through a second detent to operate a second switch contact in overtravel, momentary or latching operation. Present low current "snap dome" contactors and high current snap blade switches usually have a preload driver from button to dome, either direct with a silicone layer or nipple interface. Travel angle in such cases is usually limited to 6 degrees to full travel. More than that could damage, flatten or fracture connectors of the dome or snap blade type.